Lightning characteristics of Corsican storms with different charge structures are investigated in this study. Observations of an LMA network are used to document the total lightning activity. ...Complementary lightning observations of the lightning detection network Météorage are also used. A clustering algorithm is used to build a database of electrical cells from June to October 2018. A method is also applied to infer the vertical charge structure, as dominant dipoles, per 10‐min period for each electrical cell. As an example, one cell recorded in July 2018 is discussed. The cell database is then presented as well as the main electrical properties according to the dominant charge structures. For instance, the higher in altitude the dominant dipole, the higher the flash rate. Overall, dominant negative dipole are observed for 25% of the 10‐min periods and can be separated into two categories: (a) low altitude negative dipole class dominated by negative cloud‐to‐ground (CG) flashes with a main positive layer located between 2 and 4 km height and (b) high altitude negative dipole class, dominated by negative intracloud (IC) with a main positive layer at 5 km height. Dominant positive dipole can also be separated into two categories with (a) a dominant positive dipole located between 4.5 and 10 km high, −CG dominance, weak flash rate and (b) higher altitude dominant positive dipole, +IC dominance and a larger +CG fraction. The synergistic use of LMA and Météorage observations independently gives a rational type and polarity classification with regard to the vertical charge structure.
Plain Language Summary
Lightning characteristics of Corsican storms with different charge layers distributions are investigated in this study. Observations of the 3D lightning imager SAETTA, deployed in Corsica, are used to document the total lightning activity. Complementary lightning observations recorded by the French operational lightning detection network Météorage are also used. A algorithm is applied on the lightning data to build a database of electrical cells from June to October 2018. A method is also applied to infer the dominant dipole charge structure per 10‐min period for each electrical cell. The results show that the higher in altitude the dominant dipole, the higher the flash rate. Overall, dominant negative dipole are observed for 25% of the 10‐min periods and can be separated into two categories with low and high altitude of the dominant dipole that are associated with weak and strong flash rate. The synergistic use of the 3D lightning imager and the French operational lightning detection network gives a rational type and polarity classification to observed flashes with regard to the vertical charge structure.
Key Points
Vertical charge structures of Corsican thunderstorms and their lightning characteristics are documented based on VHF and LF observations
25% of storms 10 min‐periods showed negative dipole structures with some of them the highest flash rates recorded during the 5‐month period
Flash polarity provided by the LF lightning locating system is consistent with the inferred charge structure
Lightning characteristics of Corsican storms with different charge structures are investigated in this study. Observations of an LMA network are used to document the total lightning activity. ...Complementary lightning observations of the lightning detection network Météorage are also used. A clustering algorithm is used to build a database of electrical cells from June to October 2018. A method is also applied to infer the vertical charge structure, as dominant dipoles, per 10-min period for each electrical cell. As an example, one cell recorded in July 2018 is discussed. The cell database is then presented as well as the main electrical properties according to the dominant charge structures. For instance, the higher in altitude the dominant dipole, the higher the flash rate. Overall, dominant negative dipole are observed for 25% of the 10-min periods and can be separated into two categories: (a) low altitude negative dipole class dominated by negative cloud-to-ground (CG) flashes with a main positive layer located between 2 and 4 km height and (b) high altitude negative dipole class, dominated by negative intracloud (IC) with a main positive layer at 5 km height. Dominant positive dipole can also be separated into two categories with (a) a dominant positive dipole located between 4.5 and 10 km high, −CG dominance, weak flash rate and (b) higher altitude dominant positive dipole, +IC dominance and a larger +CG fraction. The synergistic use of LMA and Météorage observations independently gives a rational type and polarity classification with regard to the vertical charge structure.
By means of the SAETTA 3D lightning mapping array, the total lightning activity has been detected in a 240 km × 240 km square domain centred on the island of Corsica located in the West Mediterranean ...basin, and characterized by a maritime and mountainous environment, with a complex and relatively high relief. The study period covers the months from April to December of the 6 years from 2014 to 2019. Observations are reported with a horizontal resolution of 1 km and a vertical resolution of 0.1 km in terms of density of VHF sources emitted by lightning, and of number of lightning day, in plane- and vertical- projections. Vertical distributions of VHF sources are also provided monthly for the whole period and over the full domain. These 3D long term observations show that the number of lightning days is more important on the main relief of the island. The density of VHF sources exhibits a sharp maximum over the confluence area of the 3 main valleys in the center of the northern part of the island, characterized by a recurrent and vertically well developed lightning activity. The period from 11:00 UTC to 14:00 UTC in July, and in a lesser extent in June and August, is at the origin of this density maximum. This behavior is thus due to a diurnal convection. The whole lightning activity is characterized by 2 maxima in June and September. The first one is linked with the diurnal convection in phase with the maximum elevation of the Sun. The second one must be due to usual large-scale organized thunderstorm events of the fall season. The vertical distribution of VHF sources exhibits an increase in the number of VHF sources from April to August at all altitudes, as well as an increase in the altitude of the main upper peak (from 5.8 km to 10 km) and of the secondary lower peak (from 4.2 km to 6.7 km) of this distribution. From August to December, the opposite evolution appears, except that October is characterized by a strong anomaly with a single intense lower peak at 5.5 km, apparently due to 2 strong events corresponding to anomalously electrified thunderstorms. Several of these anomalously electrified thunderstorms (negative dipoles) are reported. They are all characterized by the movement of cloud cells spatially small and relatively undeveloped vertically propagating from southwest to northeast and associated with a strong transport of desert dust from the African continent. The analysis of the meteorological environment of some of the studied events allows concluding that in each of the studied cases elevated convection was triggered, above the relatively dry atmospheric boundary layer characterized by a strong convective inhibition. The low cloud liquid water content which is a key parameter of the non-inductive charging process is probably a good candidate to explain the anomalous electrification of these events.
•First 3D lightning climatology in a maritime and mountainous region.•Maximum of lightning activity mainly due to spring diurnal convection between 11:00 and 14:00 UTC.•The most intense lightning activity is located at the crossroads of the 3 main valleys.•Occurrences of anomalously electrified thunderstorms correspond to southern flows with strong transport of African dust•Convection of anomalously electrified thunderstorms triggered above the boundary layer with strong convective inhibition
